1. Field of the Invention
The present invention relates to an ultrasound diagnostic imaging apparatus.
2. Description of Related Art
In conventional ultrasound diagnostic imaging apparatus, ultrasound waves (transmission ultrasound waves) are transmitted toward a subject such as a living object by an ultrasound probe and received ultrasound waves (reflection ultrasound waves) are converted into received signals by an ultrasound probe to display an ultrasound image on the basis of the received signals. The reflection ultrasound waves include information which indicates conditions inside the subject. Therefore, it is important to obtain reflection ultrasound waves of good quality in order to obtain a good quality ultrasound image. Quality of ultrasound image can be improved by performing signal processing and the like on received signals. However, it is preferred that transmission ultrasound waves are good quality innately.
Good quality transmission ultrasound wave means to have great temporal resolution and space resolution. Among those, temporal resolution (resolution in depth direction) can be improved by making the frequency band of transmission ultrasound waves be broad.
In view of the above, U.S. Pat. No. 5,833,614 discloses a technique for adjusting pulse signals by gradually changing pulse width of driving signals (pulse signals) of pulse square wave to obtain second harmonic component that is generated by transmission of ultrasound waves in a subject in the conventional ultrasound diagnostic imaging apparatus.